Need assistance with Wix subscription plans

Hi there, my name is Dan , I am launching a small pet waste removal business and need assistance customizing my subscription plans section. I have four subscription offerings for providing dog waste removal services (weekly/monthly/bi-weekly services etc). On my page it shows the baserate subscription rates per month for each of these 4 service offerings. I say baserate, because if a customer has more than one dog, I plan on charging an additional $3 per service for each additionally dog a household has. How do I edit wix subscriptions page to allow for customer to select how many dogs they have , to automatically change their monthly subscription price at checkout? Thanks if anyone can help.-Dan